Stuart McGill has taught for some time a technique for abdominal bracing that involves “full abdominal co-contraction.” Richard Geres

writes

The basic goal of abdominal bracing exercises is to stiffen the abdominal wall with an isometric co-contraction of all the muscles around the core. With this co-contraction of muscles there should be no movement in the spine or pelvis and the abdominal wall is neither sucked in nor pushed out. The muscles involved in this co-contraction include the transverse abdominis, internal and external obliques, rectus abdominis, quadratus lumborum and erector spinae.

For a time, a group of Australian researches and physiotherapists taught a technique called “abdominal hallowing” in an effort to have people engage specific muscles of the abdominal wall (transversus abdominus). However, newer research from McGill has demonstrated that:

The brace technique improved stability by 32%, with a 15% increase in lumbar compression. The transversus abdominis contributed 0.14% of stability to the brace pattern with a less than 0.1% decrease in compression… There seems to be no mechanical rationale for using an abdominal hollow, or the transversus abdominis, to enhance stability. Bracing creates patterns that better enhance stability.

There are two important lessons to be learned from this study. First, the brace technique is definitively superior to the abdominal hollowing technique in terms of delivering stability to the lumbar spine. Second, the stiffening of the abdominal wall delivered by McGill’s abdominal bracing technique is dramatically successful in its potential to improve lumbar stability (32% improvement

Abdominal bracing - technique

1. Practice the basic components of abdominal bracing before your attempt to combine this practice with any other specific exercises. While standing in a comfortable position or lying down, initiate the movement by taking a large breath, using your diaphragm to pull air into your tummy, which should cause your tummy to expand and protrude. This is in contrast to lifting your chest when inhaling, which does not help to create more intra-abdominal pressure. Hold the breath and "brace" your abdominal muscles by contracting them as though you were going to get punched in the stomach. These are the essential requirements of abdominal bracing. Repeat this drill for several days to ingrain the movement pattern in your muscles.

2. Perform a plank to practice combining abdominal bracing with a simple exercise. Get down on the ground on your forearms and toes, with your body in a relatively straight line. Employ the principles of abdominal bracing to tighten and stabilize your core muscles, which will keep your posture rigid. Hold this position for as long as you are able to. To breathe while keeping your core tight, breathe slowly and smoothly, using the "belly breathing" technique described in step one to keep your abs braced throughout. Repeat two or three sets of 30- to 60-second holds.

3. Perform squats for a weighted abdominal bracing exercise. The best squat variations for practicing abdominal bracing are front squats or goblet squats. Hold a dumbbell in your hands at chest level, with elbows resting against your ribcage and the dumbbell touching your chest. Initiate the movement by taking a deep breath and bracing your abdominal muscles, then lower your hips while sitting back as though you were descending into a chair. Lower your butt as low as you can, ideally until your legs are completely parallel to the ground. During the upward movement exhale slowly -- but without releasing the tension in your abdominal muscles. Repeat for three or four sets of six to eight repetitions.